Earlier computers had their instructions hardwired into their physical design or held externally on punched paper tape or cards. Reprogramming them to do a different task entailed internal rewiring or altering the physical storage media. The Baby marked a new computing era, described by some as the “birth of software,” in which swapping programs was far simpler—requiring only an update to the electronic memory. Both instructions and data were held in the Baby’s memory and the contents could be altered automatically at electronic speeds during the course of computation.

In technical terms, the Williams-Kilburn tube was the earliest form of random access memory, or RAM. The Baby’s memory consisted of one of these tubes, able to store up to 1,024 bits—equivalent to just 128 bytes. In contrast, the average computer today has RAM in multiples of gigabytes, more than a billion times bigger.

The Baby was only ever intended to be a proof-of-concept rather than to serve as a useful calculation tool. So once it had shown the new memory was reliable, attention shifted to building a more powerful and practical machine using the same concepts. This resulted in the Manchester Mark 1, which in turn was the model for the Ferranti Mark 1, the world’s first computer to be sold commercially, in February 1951.

While today nothing remains of the original Baby, a working replica is on display at the Museum of Science and Industry (MOSI) in Manchester. It’s well worth a visit to reflect on just how far computing has come.